Electrochromic films of a methylcarbazole derivative: optimization of polymerization and optical contrast

The effect of the polymerization potential and time on the electrochemical and optical responses of electrogenerated films of poly-[3,6-bis(2-(3,4-ethylenedioxy)thienyl)-N-methylcarbazole] (PBEDOT-NMCz) was studied. Every electrogenerated film was characterized according to the charge consumed during polymerization, its redox charge density (calculated by integration of a control voltammogram), the efficiency of the polymerization process (defined as the charge consumed during electropolymerization to create one redox site), and its optical contrast. Within the studied polymerization potential range, 0.75 to 2 V, the charge consumed during polymerization increased with the potential, while the efficiency of the polymerization process decreased. The redox site production rate reached a maximum at 1.25 V. The optical contrast of the obtained films remained the same when polymerizing in the range between 0.75 and 1.25 V. Polymerization at more anodic potentials resulted in films of lower electrochromic quality (defined as the maximum contrast achievable). The optimal conditions for electropolymerization in terms of optimum energy consumption and the best electrochromic quality of the films were established.     

Self-assembly and electrochromic property of electroactive tetraaniline-<Emphasis Type="Italic">b</Emphasis>-PEG diblock copolymer

A kind of amphiphilic rod-coil diblock copolymer consisting both of tetraaniline (TAni) and polyethylene glycol (PEG) blocks, TAni-b-PEG, was synthesized. The diblock copolymer shows excellent electrochromic properties, especially, in switching time and coloration efficiency compared with tetraaniline. TAni-b-PEG is able to self-assemble into spherical structure, which is attributed to the formation of conducting channels and increase of ion-exchange capacity of TAni-b-PEG, implying that a block copolymer with electrochromic block and high ionic conductive block simultaneously possesses improving electrochromic properties.     

ORD and CD studies of poly[(S)(−)-N-α-methylbenzylethylenimine]

The advantages of chiral N-substituted polyethylenimines for the chiroptical study of macromolecular conformations in solution have been considered. Poly[(S)(?)-N-α-methylbenzylethylenimine] (poly-3) and five model compounds have been obtained and their chiroptical properties studied. The cyclic dimer and tetramer of imine 3 are suitable models for the chiroptical study of configurational and conformational behaviour of randomly coiled and helical poly-3 in solution. Unlike the disordered poly-3 in acidified solvents and the configurational models in various solvents, helical poly-3 in hydrocarbon solvents has positive optical rotation and positive CD-band of the tertiary amine chromophore at 223 nm. The appearance of this inherently chiral chromophore of the helix explains the observed changes of the sign and values of the optical rotation of poly-3 in various solvents which are mainly caused by conformational transformations of the main chain. The presence of helical conformations of poly-3 in solution are also confirmed by optical rotation data of stereocopolymers and the concentration dependence data of ORD curves of poly-3. This conclusion agrees with NMR and i.r.-data.     

钒钨酸盐/刚果红电致变色复合膜及器件研究

应用Layer-by-Layer自组装技术,采用聚乙烯亚胺(PEI)阳离子将无机电致变色材料[P2W15V3O62]8-(P2W15V3)阴离子与刚果红(CR)阴离子通过静电引力复合,构筑了复合膜[PEI/P2W15V3/PEI/CR]20及对比膜[PEI/P2W15V3]20.利用扫描电子显微镜、紫外-可见吸收光谱和电化学工作站研究了复合膜的形貌与电致变色性能.对比研究表明,复合膜可实现浅红色-蓝紫色-浅红色的可逆颜色调变,且保持了[P2W15V3O62]8-阴离子的电致变色性能,光反差22.55%,着色效率122.67 cm2/C.复合膜循环测试400圈后透过率(500 nm)处损耗仅为6.94%,稳定性良好;由复合膜组装的电致变色器件也实现了由浅红色到蓝紫色的颜色变化.本研究可为解决多酸电致变色材料颜色变化单一的问题提供参考.     

Synthesis and electropolymerization of 5,12-dihydrothieno[3′,4′:2,3][1,4]dioxocino[6,7-b]quinoxaline and its electrochromic properties

Synthesis of a new thiophene-based monomer; 5,12-dihydrothieno[3′,4′:2,3][1,4]dioxocino[6,7-b]quinoxaline (DDQ), was realized. The chemical structure of the monomer was characterized by ¹H NMR, FTIR and mass spectroscopy techniques. Electrochemical polymerization of DDQ and characterization of the resulting polymer [P(DDQ)] was performed. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. P(DDQ) has a low oxidation potential (0.9 V) and low band gap (1.73 eV) compared to polythiophene. In addition, dual-type polymer electrochromic device (ECD) based on P(DDQ) with poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed. Spectroelectrochemistry, electrochromic switching, stability and open-circuit stability of the device were studied. It was observed that polymer have good switching time, reasonable contrast and optical memory.     

Synthese et polymerisation du diamino-3,4 styrene: Application a une methode generale de preparation de polyvinyl-5(6) benzimidazoles

We describe a new method for preparation of 2-substituted poly-5(6) vinyl benzimidazoles starting from a new polymer, poly3,4-diaminostyrene. The monomer (3,4-diamino-styrene) is synthesized by an original 6-step process with an improved overall yield using p-aminoacetophenone. The radically induced polymerization affords the best results under emulsion conditions. The one-step transformation into poly-5(6) vinyl benzimidazole is achieved with a high degree of conversion.     

Electrochemical synthesis and investigation of poly(1,4-bis(2-(3,4-ethylenedioxy)thienyl)benzene) and its application in an electrochromic device

1,4-Bis(2-(3,4-ethylenedioxy)thienyl)benzene, prepared by Stille cross-coupling reaction was successfully electrochemically polymerized to give polymer 1,4-bis(2-(3,4-ethylenedioxy)thienyl)benzene (PEBE). Characterizations of the resulting polymer PEBE were performed by cyclic voltammetry (CV), UV–vis, Fourier transform infrared spectroscopy and scanning electron microscopy. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. The resulting polymer film has distinct electrochromic properties and shows three different colors (deep red, gray, and light blue) under various potentials. At the dedoped state of the polymer, the π–π* transition absorption peak is located at 510?nm and the optical band gap (E _g) was calculated as 1.92?eV. The PEBE film shows a maximum optical contrast (ΔT%) of 31.0?% at 500?nm with a response time of 0.85?s. The coloration efficiency of PEBE film was calculated to be 182.2?cm²C^?1. An electrochromic device (ECD) based on PEBE and poly(3,4-ethylenedioxythiophene) was also constructed and characterized. The response time was measured as 0.4?s, and the coloration efficiency of the device was calculated to be 225.4?cm²C^?1. Furthermore, this ECD exhibited satisfactory optical memories and redox stability.     

Lithium ion penetration depth profiles and reversibility of electrochromic reaction for TiO2 thin films

We investigated the penetration depth profiles of lithium ions in titanium oxide thin film during electrochromic reactions. The penetration depth profiles were obtained using time-of-flight secondary ion mass spectrometry (TOF-SIMS) for various states associated with coloring and bleaching reactions. It was found that the amount of penetrated lithium ions in the coloring process decreased sharply with increasing depth for samples in which lithium ions were inserted by applying a voltage, Vi, for 50 s in electrolyte. Over 70 % of the total lithium ions were detected within 10 nm from the surface of the film. The amount of ions in each depth was represented as a function of 1/d ² (d, depth), and the penetration depth of the lithium ions increased by increasing Vi. Furthermore, we found that the de-intercalation of the lithium ions by applying a reverse voltage arise preferentially near the surface of the film. The de-intercalated (released) lithium ion ratio seems to decrease with increasing the penetration depth. Hence, we expected that an electrochromic device using nanorod-structured titanium oxide film would improve reproducibility owing to a small number of unreleased ions. A film composed of nanorods was made by oblique evaporation. The electrochromic device using the nanorod-structured film showed excellent reproducibility for small value of driving voltage. The number of possible switching increased by a factor of 30 according to the driving voltage. In this paper, we discuss the details of the relationship between the lithium ion penetration depth profile and the electrochromic reactions.     

Electrochemical behavior of Inhcf in alkali metal electrolytes

The paper characterizes electrochemical properties of indium hexacyanoferrates (Inhcf). The cyclic voltammetric response in the presence of different metal alkali cations of divalent cations and of hydronium has been investigated. The Inhcf can exchange reversibly with all of these cations. This feature makes the Inhcf a good candidate for many electrochemical applications where a source or sink of metal cations is needed, e.g., electrochromic and energy storage devices. A prototype electrochromic system based on an Inhcf and Cohcf couple has been assembled and tested.     

Separation of hydrocarbon and sulfur-containing gases on a new poly-(1-trimethylsilyl-1-propyne)/poly-(1-phenyl-1-propyne) mixed stationary phase in the presence of water

The separation of hydrocarbons (methane, ethane, propane, n-butane, ethylene, and propylene) and sulfur-containing gases (hydrogen disulfide, sulfur dioxide, carbonyl sulfide) on a new mixed stationary phase poly-(1-trimethylsilyl-1-propyne)/poly-(1-phenyl-1-propyne) in the presence of water has been studied by gas chromatography. It has been demonstrated that the new mixed stationary phase outperforms the known polymeric adsorbents and stationary phases by resolution, asymmetry factor, and column efficiency.     

Coordinative supramolecular assembly of electrochromic thin films

The article is concerned with the layer-by-layer (LbL) assembly of electrochromic films using coordinative interactions between compounds. At first the concepts of coordinative supramolecular assembly are explained and examples are presented. Subsequently electrochromic LbL assemblies prepared upon electrostatic and/or coordinative interactions are briefly discussed. In the focus of the article are films of terpyridine(tpy)-functionalized polyiminoarylene metal ion complexes, which are prepared upon coordinative LbL assembly of the tpy-substituted polyiminoarylenes and metal ions. The films exhibit reversible electrochromic behavior with high contrast and fast response times. It is demonstrated that the electrochromic behavior of the films can be modified by a variation of polymer structure, metal ions, and counterions.     

N-substituted 2,5-Di(2-thienyl)pyrroles. Synthesis and electrochemical properties

2,5-Dithienylpyrroles containing p-substituted benzene ring at the nitrogen atom were synthesized. The formylation and subsequent crotonic condensation of N-(4-nitrophenyl)-2,5-di (2-thienyl)pyrrole was performed. Electrochemical behavior of the compounds and electrochromic properties of 2,5-di(2-thienyl)-pyrrole containing p-semidine fragment at its nitrogen atom were studied.     

Combined QCM-D/GE as a tool to characterize stimuli-responsive swelling of and protein adsorption on polymer brushes grafted onto 3D-nanostructures

A combined setup of quartz crystal microbalance and generalized ellipsometry can be used to comprehensively investigate complex functional coatings comprising stimuli-responsive polymer brushes and 3D nanostructures in a dynamic, noninvasive in situ measurement. While the quartz crystal microbalance detects the overall change in areal mass, for instance, during a swelling or adsorption process, the generalized ellipsometry data can be evaluated in terms of a layered model to distinguish between processes occurring within the intercolumnar space or on top of the anisotropic nanocolumns. Silicon films with anisotropic nanocolumnar morphology were prepared by the glancing angle deposition technique and further functionalized by grafting of poly-(acrylic acid) or poly-(N- isopropylacrylamide) chains. Investigations of the thermoresponsive swelling of the poly-(N-isopropylacrylamide) brush on the Si nanocolumns proved the successful preparation of a stimuli-responsive coating. Furthermore, the potential of these novel coatings in the field of biotechnology was explored by investigation of the adsorption of the model protein bovine serum albumin. Adsorption, retention, and desorption triggered by a change in the pH value is observed using poly-(acrylic acid) functionalized nanostructures, although generalized ellipsometry data revealed that this process occurs only on top of the nanostructures. Poly-(N-isopropylacrylamide) is found to render the nanostructures non-fouling properties.     

Deuterium NMR stereochemical analysis of threo–erythro isomers bearing remote stereogenic centres in racemic and non-racemic liquid crystalline solvents

We report the proton-decoupled deuterium NMR study of labelled diastereomers with remote stereogenic carbons dissolved in various mixtures of poly-γ-benzyl-l-glutamate (PBLG) and poly-γ-benzyl-d-glutamate (PBDG) liquid crystalline solutions. The evolution of quadrupolar splitting as well as the diastereomeric and the enantiomeric discrimination versus the proportion of PBLG and PBDG in the liquid crystalline phase is studied. It is shown that racemic liquid crystalline solutions of PBLG and PBDG may be used to measure diastereomeric excess (de). Thereafter the spectrum in PBLG solution allows for measuring the enantiomeric excess (ee) of each diastereomer. These first results suggest substantial prospects in the field of the analysis of diastereomers with remote stereogenic carbons.     

Vibrational spectra and assignment of poly-(p-phenylene sulfide) and its oligomers

Infrared and Raman spectra of poly-(p-phenylene sulfide) and some of its oligomers have been recorded. Dichroic measurements on stretched crystalline polymer films have been performed. A tentative symmetry-based assignment for the observed modes is given.The influence on the i.r. spectra of the amorphous content of polymer is also presented and discussed. Particular attention has been given to the bands affected by intrachain coupling. This is in view of the application of the spectroscopic techniques to the understanding of thedoping mechanism and transport properties of doped sulfur-containing polymers.     

Synthesis and electrochromic properties of polyimides with pendent benzimidazole and triphenylamine units

Five novel near-infrared electrochromic aromatic polyimides(PIs) with pendent benzimidazole group were synthesized from 4,4'-diamino-4'-(1-benzylbenzimidazol-2-yl)triphenylamine(named as DBBT) with five different dianhydrides via two-step polymerization process, respectively. The maximum UV-Vis absorption bands of these PIs locate at about 335 nm for solid films due to the π-π* transitions. A reversible pair of distinct redox peaks, that were associated with a noticeable color change from original yellow to blue, was observed in the cyclic voltammetry(CV) test. A new absorption peak emerged at 847 nm in near-infrared(NIR) region with increasing voltage in UV-Vis-NIR spectrum, which indicates that PI can be used as NIR electrochromic material. These novel PIs have good electrochemical stability, appropriate energy levels for the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO), in the range of-5.17 e V to-5.20 e V and-2.14 e V to-2.26 e V(versus the vacuum level) determined by cyclic voltammetry method. These values basically consisted with the results of quantum chemical calculation. These polyimides can be used as novel electrochromic and hole transportation materials.     

氧化铑变色薄膜的制备及其电变色研究

采用溶胶-凝胶方法制备了氧化铑电致变色薄膜。通过施加阴极或阳极电位, 薄膜在碱性电解液中呈现从亮黄（还原态）到深绿（氧化态）的可塑颜色变化,而 且可达到上千次循环而性能不变。采用XRD,SEM,TG,DTA,UVV,FTIR和循环伏安 等技术对薄膜的晶态、形貌、热处理过程和电变色过程进行了研究。得出100 ℃处 理的膜内含有一定量的结晶水,其性能最好。对薄膜的电致变色性能如：着色效率 、响应时间及循环寿命、开路记忆等进行了测试,并讨论了氧化铑薄膜电变色的反 应机理。     

Synthesis, photophysical, and electrochromic properties of new triarylamino-containing polyphenylquinoxalines

New triarylamino-containing bis(α-diketones) are synthesized. On the basis of these compounds, a series of electrochromic organosoluble polyphenylquinoxalines with glass-transition temperatures of 224–315°C are prepared. All polymers intensively fluoresce in solutions and thin films with maxima at 535–600 and 530–560 nm, respectively. Cyclic voltammograms of polyphenylquinoxalines exhibit reversible redox properties in the range E _1/2 = 0.92–1.25 eV. It is shown that, after 15 cycles, all polymers preserve high stability and reversibility of electrochromic characteristics, but their color changes from yellow (neutral form) to wine red (oxidized form).     

Kinetics of electron transfer reactions of metal complexes at impermeable redox active polymeric films on electrode surfaces and charge transport within the polymer film

At rotated Pt disk electrodes coated with thin films of the redox polymer poly-[Ru(vbpy)₃]²⁺, ruthenium and iron bipyridine complexes dissolved in acetonitrile can become oxidized by two pathways. The first is diffusion of the solute complex through the polymeric film to react at its normal potential E_sub⁰, at the Pt/polymer interface. The second is a mediated electron transfer cross-reaction between the solute complex and poly-[Ru(vbpy) ₃]²⁺ sites generated in the film at adequately positive potentials. The mediated reaction, as judged from the lack of variation of its rate k_crsΓ with the quantity of polymer mediator sites present in the multimolecular layer film, and from other evidence, is confined to the outer few (one?) monolayers of ruthenium polymer film sites. The mediated reaction becomes the dominant pathway for films with Γ_T ～2×10^?9 mol/cm² of ruthenium polymer sites, owing to the low permeability (measured independently) of the solutecomplexes into the film. The rate k_crsΓ could be measured when the solute complex oxidation potential is more positive than that of the redox film, and is too fast to measure when E_sub⁰, is more negative than the redox film E_cal?⁰, New theory is presented and evaluated to describe the rising portions of the voitammetric waves for the nine solute complexes studied. The rate of charge transport through the poly-[Ru(vbpy)₃]²⁺ film becomes controlling under certain conditions and can be thereby measured as well.